Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

Musty Smell In A/c

airman1, i have been reading the posts on musty smells in a/c systems as i have the similar problem with my in the attic unit. i have a hydro air system, triple by-pass 1 1/2 years old in my new house. this is the first time i have ever had this problem and the first time i have a split system with a unit in the attic. i am in massachusetts. i have checked out the attic...no problems,
i have checked out the unit along with my son-in-law and its sealed good.
my son-in-law has been in the hvac line for at least 20 years and hasn't heard about the dss problem and either have i. i have had 4 new houses so far in my time, i'm 63 yrs old. my son-in-law cleaned the coils and the system ran with no smell. the next day the smell was back. when we open the attic pull-down stair and start up the ladder you can smell the musty oder slightly.
you talked about coating the coils...what is the coating? will any coating work?? i'm in the process of investigating so i only have to do somthing once to fix this. sounds like coating the coils works best. i did think about installing an exhaust fan....my house is new with the typical ridge and soffit vents with proper venting but coating the coils sounds like the way to go. we don't hear of this problem in my area but i'm sure its out there. you don't happen to know of any coating places around massachusetts do you??????

thanks,

pete

ps,

i'm in the design field drawing plans for commercial & residential buildings.

A musty smell can be caused by several things, but usually begins with standing water. Since you are in a Norhtern climate, it is doubtful that issues that airman1 encountered are precisely the same as what you are seeing.

I'm not sure I understand your system. Is this a hydronic coil that has hot water flowing through it from a boiler or other type of water heater? Is there a heat pump involved? Please describe "triple by-pass". Having 8 stents in my heart, triple by-pass is a scary term for me.

If the same smell is in the attic that your complaint is, that attic unit isn't sealed as good as you think. With DSS, if the coil is cleaned, the smell won't be back the next day. It will come back, just not that quick. I'd look real close at everything in that attic, including the panels on the unit. JMO.

If everything was always done "by the book"....the book would never change.

my unit is a wel-mclain boiler model uo-4 series 1, 146,000btu with a becket burner, the attic evaporator unit is a first co. triple by-pass from what i'm told means the air travels over the coils 3 times before being sent thru the ducts. i can see why triple by-pass is a scary term to you robo-teq, i hope you are doing well.......i have a couple of friends with stents and they are doing real good...
when we took the panels off the unit everything was good , the panels and the unit itself wasn't fouled up with mold.
another idea would be to get some more air movement in the attic by installing a exhaust fan what do you think???
the attic smell was stuffy with a very slight must odor when its hot outside.
the local hvac suppliers have a coated unit but coated for rust and corrosion and they haven't heard of this problem altho they sell ulta-violet lights and a spray called bio-tech.
i checked all over the attic and around the unit and i find nothing to indicate standing water or wetness.......
i guess thats why i figured the dss was a coil thing.... i hope this info helps.

condensate line is piped to outdoors not sewer line...
i must amend a statement i made.....when the coils were cleaned last week and the odor was not there we didn,t need a/c for 3-4 days but when turned on the odor was there. i previously said the next day but it was 3-4 days.
my problem really sounded like the situation airman1 was talking about.
would a coating used to inhibit rust and corrosion work like what airman1 was talking about or is the coating something special???

condensate line is piped to outdoors not sewer line...
i must amend a statement i made.....when the coils were cleaned last week and the odor was not there we didn,t need a/c for 3-4 days but when turned on the odor was there. i previously said the next day but it was 3-4 days.
my problem really sounded like the situation airman1 was talking about.
would a coating used to inhibit rust and corrosion work like what airman1 was talking about or is the coating something special???

pete

From reading the many posts by airman1 it seems that his applications to problems are mostly localized to areas having continuous high temperatures and humidity. Airman1 also did not deal with hydronic coil heating at all, due again to his locale.

It would seem that you should be looking for issues other then what airman1 contended with. You are in a completely different type of environment with a completely different set of issues.

If the smell is coming from your cooling systems evaporator coil, it may be a matter of it simply not dropping to a low enough surface temperature to retard mold growth. If this is the case, you should have your HVAC technician look into possibly lowering the blower speed enough to resolve the issue. There are ways of lowering blower speeds that will not create freeze up problems. Only with an on-site inspection of your specific equipment can the proper way to lower blower speed be determined. Specific anti-freeze protection controls may also need to be installed.

thanks for the input.....
i found out this item this morning that might be interesting...
when the coil was cleaned it was cleaned from one side because the ducts were in the way on the other side....is it possible the spray could reach the other side????i don't know stuff concerning hvac...or is it likley the build-up is on the un-seen side.......might have to cut an access in the duct???? or is it easy to take the coil out to clean both sides????

Operating the fan in the "on" mode dries the coil/pan. Drying kills microbial growth. I operate my fan continuous "on" to eliminate musty odors. Several hours per day may prevent the build-up of biological growth in the coil and ducts. This does raise the %RH slightly. I have 90 pint dehu to maintain 50%RH throughout my home. Regards TB